AMBIGUOUS RESULTS

Cellectar's iopofosine data show 15.4% response rate in myeloma Phase 1

A published dose-escalation study in heavily pretreated myeloma patients set a maximum tolerated dose and pointed to a fractionated regimen for further testing, six years after the trial finished enrolling.

By AppliedXLJuly 15, 2026Trial NCT02278315

Executive Summary

A peer-reviewed journal published Phase 1 dose-escalation results for Cellectar's radiopharmaceutical iopofosine I 131 in heavily pretreated multiple myeloma, years after the trial itself finished.
The study found a maximum tolerated dose, manageable hematologic toxicity, and modest but dose-dependent antitumor activity in a population that had exhausted other options.
The publication recommends a fractionated dosing regimen the sponsor's ongoing programs would need to test to build on the single-dose activity seen here.
Iopofosine's lipid-raft targeting mechanism sits apart from the BCMA-directed antibodies and cell therapies that dominate current myeloma development, but that isolation reflects a sparse field for this modality, not validated differentiation.

The publication

Cellectar Biosciences, Inc. announced the Cancers journal publication of a Phase 1 dose-escalation trial of iopofosine I 131, a radiotherapeutic that targets lipid rafts on cancer cell membranes, combined with low-dose dexamethasone in 31 patients with relapsed or refractory multiple myeloma who had exhausted a proteasome inhibitor and an immunomodulatory drug. The trial, registered as NCT02278315, enrolled between February 2015 and completed in August 2022, with a primary completion date of December 9, 2020. Its stated primary outcome measure was the number of participants with dose-limiting toxicities, the standard endpoint for a Phase 1 dose-finding study. Cellectar+1

The result: MTD and a fractionated regimen

Among 26 patients evaluable for efficacy, the study established a single-dose maximum tolerated dose of 31.25 mCi/m² and recommended moving forward with a fractionated Phase 2 regimen of 15 mCi/m² given on days 1 and 7 alongside weekly low-dose dexamethasone. Stable disease or better was reported in 84.6% of evaluable patients, and the overall response rate across the group was 15.4%, with four patients achieving partial responses. Among the subset of ten patients who received at least 60 mCi of total dose, the overall response rate rose to 30%, consistent with the dose-dependent activity investigators described. Sikander Ailawadhi, M.D., of the Mayo Clinic and the publication's lead author, said the study "demonstrated manageable toxicity with adverse events being essentially limited to cytopenias, encouraging disease control, and evidence of antitumor activity in a heavily pretreated population". Cellectar

Safety and tolerability

Investigators reported a favorable and manageable safety profile, with adverse events consisting primarily of predictable, reversible hematologic toxicities, and no new safety signals emerged. Because the primary endpoint was dose-limiting toxicity rather than an efficacy measure, the trial's core information value is tolerability: whether the regimen can be dosed and, per the publication, whether recovery of cytopenias over time supports repeat dosing in future development, a question the recommended fractionated schedule is designed to test. Cellectar

Registry history behind the publication

The registry record shows this result followed a period of limited activity: the trial's status moved to Unknown status in April 2022 before reverting to Active, not recruiting in July 2022, when enrollment was also revised down from an anticipated 33 to an actual 31 and the primary completion date was adjusted from April 2020 to December 2020. The trial was marked Completed in February 2023, more than two years after its primary completion date, and this publication followed more than three years after that. The result itself, not the registry timeline, carries the substance of this event: a Phase 1 dataset that had already fully enrolled and completed is now formally reported in the literature. NCT02278315

Where iopofosine sits in myeloma

Multiple myeloma drug development is dominated by BCMA-directed mechanisms: bispecific antibodies such as Pfizer's elranatamab and Regeneron Pharmaceuticals' linvoseltamab, GlaxoSmithKline's antibody-drug conjugate belantamab mafodotin, and CAR-T therapies including Janssen's ciltacabtagene autoleucel and Celgene's idecabtagene vicleucel, all now in Phase 3 or Phase 4 testing. Iopofosine's lipid-raft-targeting radiotherapeutic mechanism has no other active trial studying that target in multiple myeloma, and only 11 trials across the indication have used a radiopharmaceutical modality at all. Cellectar's own Phase 2 CLOVER-1 study of iopofosine in Waldenstrom macroglobulinemia already reported positive 12-month follow-up data in May 2026, with a 61.8% major response rate and 83.6% overall response rate in that population, which sets a higher efficacy bar than the 15.4% response rate seen in this myeloma cohort.

This analysis was produced using AI-assisted reporting systems, AppliedXL data, and official public records. These systems undergo editorial review, quality checks, and regular audits by human experts. Errors may still occur, as with any automated system. Always consult the linked primary sources. Read our AI Editorial Policy.